Splinter resistant composite laminate

ABSTRACT

A composite component includes splinter arrestors laminated transverse to the fiber orientation of an outermost composite material layer. The splinter arrestors are located upon the outermost composite material layers at a predetermined distance from each other to constrain a splinter of fibers from the outermost composite material layers to an acceptable length.

[0001] This invention was made with government support under ContractNo.: DAAH10-98-2-0001 awarded by the Department of the Army. Thegovernment therefore has certain rights in this invention.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to fiber reinforced resin matrixcomposites and, more particularly, to a composite laminated structurewhich resists splintering typical from ballistic impacts.

[0003] Articles fabricated from fiber reinforced resin matrix compositematerials, e.g., Kevlar, graphite, and fiberglass, are known and havefound increasing use in load bearing structural applications due totheir high strength, light weight, and ability to be fashioned intocomplex shapes. Such composite structural materials are particularlysuitable for aircraft structures.

[0004] A composite component is typically formed through a lay-up ofcomposite material layers. The lay-up technique employs the use of amultiple of discrete plies of a substrate material having a plurality ofparallel fibers that are impregnated with a resinous material. Themultiple of layered plies are laminated in a mold and then placed in anautoclave or oven for application of heat and pressure such that thelay-up cures into the finished composite component.

[0005] To maximize the benefits of composites, it is essential that thefiber orientation be optimally tailored to meet the strength andstiffness requirements for a particular application. Disadvantageously,the outermost layers or plies of the composite component include asingle fiber orientation, which may be subject to splintering or peelingin response to impact hazards. Since composites have relatively lowinterlaminar peel strength, the splinters may become relatively long.These elongated splinters may compromise structural integrity. Arelatively small puncture may thus damage a relatively larger area. Evenif integrity is not an issue, the repair covers a large area throughwhich the splinter extends.

[0006] Accordingly, it is desirable to provide a composite laminatewhich resists splintering when damaged particularly from ballisticimpact.

SUMMARY OF THE INVENTION

[0007] The composite component according to the present inventionincludes splinter arrestors laminated transverse to the fiberorientation of an outermost composite material layer.

[0008] The splinter arrestors are tows located upon the outermostcomposite material layers at a predetermined distance from each other.The predetermined distance is a distance which will constrain a splinterof fibers from the outermost composite material layers to an acceptablelength. Alternatively or in addition, tows may be eliminated insubsurface layers to avoid an increase in the overall weight of thecomposite component.

[0009] The present invention therefore provides a composite laminatewhich resists splintering when damaged, particularly from ballisticimpact.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiment. The drawings thataccompany the detailed description can be briefly described as follows:

[0011]FIG. 1 is a general exploded view of a composite component;

[0012]FIG. 2 is a general perspective view of a single tow of aplurality of fibers;

[0013]FIG. 3 is a general perspective view of a composite componentillustrating splinter arrestors according to the present invention; and

[0014]FIG. 4 is a general exploded view of another composite componentwith subsurface tows which correspond to the splinter arrestorseliminated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0015]FIG. 1 illustrates an exploded view of a composite component 10manufactured from a plurality of prepreg composite material layers 12which are selectively oriented and selectively chosen to achieve thedesired strength. The plurality of prepreg composite material layers 12may be laid up upon each other or may skin a core material 14 such ashoneycomb, foam, or the like. The actual lay-up of one or more prepregsis well known and further description of the details thereof need not beprovided herein.

[0016] Each material layer 12 is preferably manufactured ofunidirectional fiber material which is laid down as a plurality ofparallel tows. That is, each material layer 12 includes a plurality oftows 12 t (FIG. 2) which are manufactured as a bundle of continuousmonofiber strands. As will be apparent, each tow or tow strand isessentially a bundle of a plurality of fiber filaments. Suitable fibersinclude high strength fibers such as graphite fibers, fiberglass fibers,ceramic fibers, and aramid fibers, which are commercially available. Theoutermost composite material layers 12′ define a single fiberorientation which may be subject to splintering or peeling in responseto damage. That is, one or more tows may be peeled away from asubsurface layer.

[0017] To prevent peeling of the outermost composite material layers 12′splinter arrestors 16 are located transverse to the single fiberorientation of the outermost composite material layers 12′. The splinterarrestors 16 are preferably individual tows oriented perpendicular tothe direction of the tows 12 t within the outermost composite materiallayers 12′ (FIG. 2). Suitable splinter arrestors 16 include highstrength fibers such as graphite fibers, fiberglass fibers, ceramicfibers, and aramid fibers, as well as lower strength fabric tape, wovencloth, and/or nonwoven fabric of interbonding fibers. Fiber placementmachines are preferably utilized to locate single splinter arrestor tows16 t upon the outermost composite material layers 12′. Relatively widertows, multiple tows, or tapes will also benefit from the presentinvention. The outermost layer is formed as a checkerboard-like pattern.It should be understood that various automated and hand layup methods oflayer and splinter placement will benefit from the present invention.

[0018] The splinter arrestors 16 are located upon the outermostcomposite material layers 12′ at a predetermined distance from eachother. The predetermined distance is preferably a distance, which willconstrain a splinter of fibers from the outermost composite material,layers 12′ to an acceptable length should a projectile p damage thecomponent 10 (FIG. 3). The acceptable length will typically depend atleast upon the composite component 10 size and location within acomposite structure.

[0019] Referring to FIG. 4, tows 12 t′ in subsurface layers whichcorrespond to the splinter arrestors 16 may be eliminated such that theoverall weight of the composite component 10 is not increased.Preferably, the tows 12 t′ which are oriented in the same direction andare directly below the splinter arrestors 16 are eliminated. Theeliminated tows 12 t′ need not be immediately below the outermostcomposite material layers 12′ but may be within a deeper subsurfacelayer within the composite component 10′.

[0020] The foregoing description is exemplary rather than defined by thelimitations within. Many modifications and variations of the presentinvention are possible in light of the above teachings. The preferredembodiments of this invention have been disclosed, however, one ofordinary skill in the art would recognize that certain modificationswould come within the scope of this invention. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described. For thatreason the following claims should be studied to determine the truescope and content of this invention.

1. A composite component comprising: a plurality of composite materiallayers comprising an outermost layer having a plurality of non-metallictows, each of said non-metallic rows separated by a first distance; andat least two non-metallic splinter arrestors laminated to said outermostlayer of said plurality of composite material layers, said at least twonon-metallic splinter arrestor arrestors oriented substantiallytransverse to a fiber direction of said outermost layer, said at leasttwo non-metallic splinter arrestors separated by a second distancegreater than said first distance.
 2. The composite component as recitedin claim 1, wherein said at least two non-metallic splinter arrestorsand said non-metallic tows are formed of graphite fibers.
 3. Thecomposite component as recited in claim 1, wherein said splinterarrestor comprises a tow.
 4. The composite component as recited in claim1, wherein said splinter arrestor comprises a monofilament.
 5. Thecomposite component as recited in claim 1, wherein said splinterarrestor comprises a fabric tape.
 6. The composite component as recitedin claim 1, further comprising a subsurface composite material layer ofsaid plurality of composite material layers below said outermost layer,said subsurface layer having a plurality of non-metallic tows and atleast two gaps separated by said second distance, said two gaps locateddirectly below said at least two splinter arrestors.
 7. A method ofmanufacturing a composite component comprising the steps of: (1)laminating at least two non-metallic splinter arrestors to an outermostlayer of a plurality of composite material layers, the at least twosplinter arrestors substantially parallel to each other and transverseto a non-metallic fiber direction of the outermost layer to limitpeeling of the outermost layer to the distance between the at least twosplinter arrestors in response to a projectile passing through thecomposite component.
 8. A method as recited in claim 7, wherein saidstep (1) further comprises laminating a plurality of relatively parallelsplinter arrestors spaced a predetermined distance from each other tothe outermost layer, the predetermined distance greater than a firstdistance between each of a plurality of twos in the outermost layer. 9.A method as recited in claim 7, wherein said step (1) further compriseseliminating tows in a subsurface composite material layer whichcorrespond in orientation to the splinter arrestor.
 10. A method asrecited in claim 7, wherein said step (1) further comprises eliminatingtows in a subsurface composite material layer which are parallel to andbelow the splinter arrestor.
 11. The composite component as recited inclaim 1, wherein said at least two non-metallic splinter arrestors andsaid non-metallic tows are formed of fiberglass fibers.
 12. Thecomposite component as recited in claim 1, wherein said at least twonon-metallic splinter arrestors and said non-metallic tows are formed ofceramic fibers.
 13. The composite component as recited in claim 1,wherein said at least two non-metallic splinter arrestors and saidnon-metallic tows are formed of aramid fibers.
 14. A composite componentcomprising: a plurality of composite material layers comprising anoutermost layer having a plurality of tows, each of said tows separatedby a first distance; and a plurality of splinter arrestors laminated tosaid outermost layer of said plurality of composite material layers,said plurality of splinter arrestors oriented substantially transverseto said plurality of tows of said outermost layer, at least two of saidplurality of splinter arrestors separated by a second distance greaterthan said first distance to limit peeling of the outermost layer to saidsecond in response to a projectile passing through the compositecomponent.
 15. The composite component as recited in claim 14, whereineach said plurality of non-metallic splinter arrestors are fabric tapes.16. The composite component as recited in claim 14, wherein each saidplurality of non-metallic splinter arrestors and each of said pluralityof tows are manufactured from non-metallic monofiber strands.
 17. Thecomposite component as recited in claim 16, wherein each said pluralityof splinter arrestors are tows.
 18. The composite component as recitedin claim 16, wherein each said plurality of splinter arrestors arcsingle monofilament.